Through my U.S. Pat. No. 4,587,688, I introduced the concept of a non-contacting dryer using a sonar-type proximity detector to control the position of an air nozzle relative to the surface of a wet vehicle after a laundering operation. My patented sonar-type proximity detector is distinguished from prior art proximity detectors used then and now in vehicle laundering systems in that the sonar transducer emits a signal toward the surface of the vehicle and receives a reflection from that surface as an essential part of its operation. The prior art systems for achieving touchless proximity detection and control of dryer components were typically of the electric-eye type in which the transducer system comprises discrete transmitter and receiver components which are aimed at one another across the wash lane. When the vehicle interrupts the optical transmission between the transmitter and the receiver, the system is set up to move the controlled component through a distance increment; if the optical transmission path is reestablished, the controlled element is deemed to be in a satisfactory position; if the transmission path is not reestablished, the controlled element is moved through another increment.
The embodiment of my invention disclosed in U.S. Pat. No. 4,587,688, the disclosure of which is incorporated herein by reference, includes a sonar transducer mounted on a relatively long nozzle support arm, one end of which is pivotally mounted overhead the vehicle and the other end of which carries the dryer nozzle. Because the pivot arm and the sonar transducer mounted on that arm move through an arc rather than a rectilinear path, some attention must be given to the matter of maintaining the proper aiming angle of the transducer toward the detected vehicle surface. By way of example, the proper aiming angle may be achieved by pivotally mounting the transducer on the arm itself or by using a transducer arrangement which produces a wide angle of sensitivity.